An electron microscope as a powerful tool for microscopic appearance observation is applied to the fields of metallurgy, mineral, chemical industry, medicine, biology, biomedicine, food, nano material and the like more and more rapidly and widely. The electron microscope mainly includes a transmission electron microscopy and a scanning electron microscope. The transmission electron microscopy (TEM) uses a focused electron beam as an illumination source, and adopts a film sample transparent to the electron beam to analyze a microstructure in the sample by an image formed by a transmission electron beam or diffraction electron beam penetrating through the sample. The scanning electron microscope uses a high energy electron beam reflected by secondary electrons to scan the sample so as to excite all kinds of physical information. Observation for two-dimensional structure and morphology on a surface of a testing sample is obtained through reception, amplification and image display of the information.
An entire electron optical part of the microscope is completely arranged in a microscope tube, and an electron gun, a collecting lens, an objective lens, an intermediate lens, a projection lens, an observation room, a fluorescent screen, a charge coupled device (CCD) and the like are arranged sequentially from top to bottom, wherein an illumination system composed of the electron gun, the collecting lens and the like provides a beam of light source with high brightness and good coherence for an imaging system. The electron gun is composed of a cathode, a control electrode (gate) and an anode. Electrons emitted by the cathode after heated at high pressure in vacuum obtain high kinetic energy to form a directional high-speed electron flow (electron beam). In a certain range, the larger the current of a filament is, the higher the temperature of the filament is, the more the emitted electrons is, and the faster the evaporation of the surface of the filament is. Thus, the filament has certain life. For example, a tungsten filament has a life of 100-150 hours generally, a lanthanum hexaboride filament has a life more than 1000 hours and a cerium hexaboride filament has a life of about 1500 hours. The filaments need to be replaced frequently.
When the filament of the electron microscope is replaced, a position of the filament is also defined very strictly: a filament tip is required to be located in a center position of the electron gun. If the position of the filament is offset, it is easy to that the brightness of the filament is dark, and operators need to enhance the brightness by increasing the bias or current, thereby damaging the filament. At present, the filament is replaced by means of hands completely, so that not only a large amount of time of instrument managers is wasted, but also manual vision disparity may cause the bias of an installation position of the filament during regulation since the filament tip and a center of a grid cap hole are not in a same plane, influencing use quality of microscopic imaging to different degrees. Meanwhile, due to a difference of manufacturers and a difference of filament types, different filaments of the electron microscope have different filament positioning seats and filament bases. When different types of filaments are positioned, different fixed installation modules need to be adopted for installing and regulating the filaments, causing time and labor consumption, low efficiency, and difficulty in ensuring positioning precision while causing resource waste.